In general a speed of a motor for driving a cooking utensil such as a mixer is varied depending upon ingredients to be processed. However in the conventional cooking only the indication of rotational speeds such as "high, medium and low" or "numerals from 1 to 10" are marked upon the casing thereof. Therefore the speed of the cooking utensil must be selected depending upon an optimum speed found in a cookbook or the like for ingredients to be processed. However, this method is very cumbersome so that the ingredients are often processed at a random speed. Furthermore a cooking utensil in which two variables such as rotational speed and processing time can be controlled is known. However, these two controlled variables are generally independently marked upon the casing of the cooking utensil so that the correlation between these two controlled variables cannot be seen. The two controlled variables must be also selected with reference to a cookbook. This method is further very cumbersome.